I am getting 3.90 gears installed soon into a 1993 GT with a T-5, and was wondering what speedo gear and carrier i would have to use. I was also wondering how accurate the speedo will actually be afterwards. Thanks
you need a 23 tooth white gear. that gear is for 3.55s. anything 90+ with above 3.55s you have to use the 3.55 gear. there is no 90+ calibration gear for 3.73s, 3.90s, or 4.10s in T-5. im not sure on how accurate it will be, i would say 3-6 mph at most
screw that 23 tooth gear, it won't be accurate or dependable. Change out your drive gear to a 6 tooth. I lucked out, my 90 has a 7 tooth already, so I can run a red 21 tooth with my 373's. (90+ has an 8 tooth drive gear)
1983-89 V8 Mustang w/T5 Trans. & 1996-98 Cobra with T-45 Trans. Use a 7 Tooth Drive Gear.
1990-95 V8 Mustang w/T5 Trans. & 1996-98 Mustang GT w/T-45 Trans. Use an 8 Tooth Drive Gear.
Here's the formula.......
Driven Gear Teeth= Drive Gear Teeth x Axle Ratio x Tire Rev. Per Mile Divided by 1000
Ex. 7 x 3.73 x 815(225/60R15) Divided By 1000 = 21.3 (Diven Gear Teeth)
Like mentioned already your going to have to change your drive gear and your best bet will most likely be to run a 6 tooth combined with the black 20 tooth gear (Used With 4.10's)The Ford Part Number is C1DZ-17271-A. The only problem is 6 Tooth is kind of odd ball so a 7 Tooth may be your only way to go and will require the Red 21 Tooth Gear (Used with 3.73's) The Ford Part Number is C4OZ-17271-A.
For the Automatic Guy's out there the drive gear I belive is machined into the output shaft. Changing the drive gear unfortunatly require's a new output shaft. Most AOD's have a 7 or 8 Tooth Drive Gear.
It won't be perfect but it will be reasonably close. Probably 4-8MPH Off.
6 Tooth isn't terribly odd ball....it's just not as common as the 7 and 8 tooth.
If noone will look at the link then I'll just post the chart, W/ 3.90 gears you'll need a 6 tooth drive and a pink 19 tooth speedo gear. 50resto.com has both gears. You can use the other link I posted to calculate gear ratio and tire size for the correct combo.
Manual Transmissions with 6 Tooth Drive Gear
Not found in OEM applications
Item Number
Description
N/A
3.08 Gear Ratio / Not possible
C0DZ-17271-A
3.27 Gear Ratio / Maroon 16 Speedo Gear
C3DZ-17271-C
3.55 Gear Ratio / White 17 Speedo Gear
C0DD-17271-B
3.73 Gear Ratio / Yellow 18 Speedo Gear
C0DZ-17271-B
3.90 Gear Ratio / Pink 19 Speedo Gear
C1DZ-17271-A
4.10 Gear Ratio / Black 20 Speedo Gear
C4OZ-17271-A
4.30 Gear Ratio / Red 21 Speedo Gear
Manual Transmissions with 7 Tooth Drive Gear
1983-1989 T-5 OEM
Pre 1993 T-5 Aftermarket
1996-1998 Cobra T-45 OEM
All Tremec Transmissions
Item Number
Description
C0DZ-17271-A
2.73 Gear Ratio / Maroon 16 Speedo Gear
C0DD-17271-B
3.08 Gear Ratio / Yellow 18 Speedo Gear
C0DZ-17271-B
3.27 Gear Ratio / Pink 19 Speedo Gear
C1DZ-17271-A
3.55 Gear Ratio / Black 20 Speedo Gear
C4OZ-17271-A
3.73 Gear Ratio / Red 21 Speedo Gear
Jeep Part #j3167393
4.10 Gear Ratio / White 23 Speedo Gear
Manual Transmissions with 8 Tooth Drive Gear
1990-1995 T-5 OEM
1996-1998 T-45 OEM Except Cobra
Item Number
Description
C0DD-17271-B
2.73 Gear Ratio / Yellow 18 Speedo Gear
C1DZ-17271-A
3.08 Gear Ratio / Black 20 Speedo Gear
C4OZ-17271-A
3.27 Gear Ratio / Red 21 Speedo Gear
Jeep Part #j3167393
3.55 Gear Ratio / White 23 Speedo Gear
Jeep Part #j3167393
3.73 Gear Ratio / White 23 Speedo Gear (Not 100% accurate. This combination will offer the best accuracy without changing the drive gear. Change drive gear to a 6 tooth for complete accuracy. See 6 tooth table.)
Jeep Part #j3167393
4.10 Gear Ratio / White 23 Speedo Gear (Not 100% accurate. This combination will offer the best accuracy without changing the drive gear. Change drive gear to a 6 tooth for complete accuracy. See 6 tooth table.)
Automatic Transmissions with 7 Tooth Drive Gear
1983-1989 Automatic Transmissions
Item Number
Description
D0AZ-17271-A
2.73 Gear Ratio / Blue 16 Speedo Gear
C7AZ-17271-B
3.08 Gear Ratio / Gray 18 Speedo Gear
C7VY-17271-A
3.27 Gear Ratio / Tan 19 Speedo Gear
C8SZ-17271-B
3.55 Gear Ratio / Orange 20 Speedo Gear
D0OZ-17271-B
3.73 Gear Ratio / Purple 21 Speedo Gear
Jeep Part #j3167393
4.10 Gear Ratio / White 23 Speedo Gear
Automatic Transmissions with 8 Tooth Drive Gear
1990-1998 Automatic Transmissions
Item Number
Description
C7AZ-17271-B
2.73 Gear Ratio / Gray 18 Speedo Gear
C8SZ-17271-B
3.08 Gear Ratio / Orange 20 Speedo Gear
D0OZ-17271-B
3.27 Gear Ratio / Purple 21 Speedo Gear
Jeep Part #j3167393
3.55 Gear Ratio / White 23 Speedo Gear
Jeep Part #j3167393
3.73 Gear Ratio / White 23 Speedo Gear (Not 100% accurate.)
Jeep Part #j3167393
4.10 Gear Ratio / White 23 Speedo Gear (Not 100% accurate.)
Now if you really want to change the internal drive gear of your manual tranny you can match it according to the table below. Be aware that the 6 tooth will offer the most combos for numerically higher gear ratios and offer the greatest degree of accuracy. The 6 tooth gear selection table for a manual tranny is the first in the page.
Item Number
Description
E3ZZ-17285-B
6 Tooth Internal Drive Gear / Black
thanks alot, have not been able to find the 3.90 gear specifically, but the pink gear on 50resto says that it goes with 3.27 gears, and dosen't come in a 90-93.
What size tires you running? 50resto has them listed by what drive gear came in the cars as per their year model. A 6t drive gear was not in any Mustangs from the factory, They are talking about a 7t drive w/ the 19t being for 3.27's. At this point you don't need to worry about the year models. You're doing something custom like putting in 3.90's, so you just need to put in the right combo of speedo gears according to your new R&P and tire size to make the speedo correct.
What I did was use both the chart and the calculator to double check what I would need, if you're running a different tire size then it can change. I then checked the speedo/drive gears in my car to make sure of what was in there. Sure enough, my 90 would have originally came w/ an 8t drive. The trans has been replaced because it has a 7t drive which allowed me to just replace the speedo gear and not have to mess w/ the drive gear.
yea the speedo gear is located in the driver side part of the tailshaft, but i don't think you take the whole thing apart, but i may be wrong. On 50resto.com they have a instruction thing, and its says just pull the one thing off, put the new gear in and put it all back together
yes you are right. there is a speedometer gear that is on the speedo cable. then there is the drive gear that is inside the tranny that turns the speedo gear. the 19tooth they are talking about is the speedo gear, piece o cake to install. HOWEVER, the 6tooth is the drive gear that i think you have to swap...i just dont feel like reading the whole thread again. to change that gear, i think you have to pull the tailshaft or some kinda surgery